There have been image forming apparatuses such as a multi function peripheral (hereinafter referred to as “MFP”) and a printer. The image forming apparatus includes a developing device that stores a developer. The developing device includes a developing roller. If air enters the developing device according to rotation of the developing roller, pressure in the developing device rises. If the pressure in the developing device rises, the air including toner in the developing device sometimes blows out to the outside of the developing device. If the air including the toner blows out to the outside of the developing device, the toner scatters to the outside of the developing device. Functional components such as a charger are likely to be stained.